Wait didn't they start working on C3 back in 2015 ? Besides, they wouldn't be posting screenshots of their work if it is supposed to be released after 1 or 2 years, its just doesn't make sense.
To be safe, it would be possible if they release it on 2018 knowing that Scirra might release it dependent on future build updates but it's kind of doubtful they will release it this year without being incomplete.
It absolutely makes sense, if you try participating in other game engine beta testing or pre-launches... You'll notice that they market it in this sequence, (website -> teasers(screenshots) -> alpha test -> beta test -> final release...
Gaps between the alpha and beta and final release sometimes takes a year or more.